Climate change in Northeast China between 1849 and 2008

At the treeline, tree growth rate is known to be very sensitive to climate change. Width of tree rings is often used to estimate climatic conditions when direct measures of temperature and precipitation at the site are unavailable. In this study, tree ring data and available site-specific climatic data were analysed and correlated to reconstruct historical temperature changes from 1849 to 2008 at the Changbai Mountain treeline. One hundred and seventy-five Betula ermanii trees were selected from seven plots at the upper treeline area on the north-facing slopes of the Changbai Mountains. Two hundred and ninety-one tree ring cores were extracted from these trees to develop the B. ermanii chronology. The tree ring width index was found to be significantly related (R ² = 0.43, p < 0.01) to the mean annual temperature at the Tianchi weather station nearby during the period of 1953–2008. A transfer function was developed from the relationship to reconstruct the mean annual temperature from 1849 to 1952, for which a climatic record at Tianchi were unavailable. The results suggest a wavelike temperature increase with alternations between rapid warming and gentle cooling periods at the Changbai Mountains treeline for the 160 years. In Northeast China, the temperature has increased 0.07 °C per decade with significant fluctuation (p < 0.05, SD = 0.64) according to the extrapolated data. The extrapolation is based on the relationship between the Tianchi station and the other 164 weather stations throughout the Northeast. Temperature increase would significantly affect the sustainability of the alpine ecosystems in the Changbai Mountains as well as the agro-ecosystem management of the Northeast China Plain, a designated farmland area for crop production by the Chinese government.